Abstract

The direct bromination of methane offers a quite selective (>98 %) route towards methane activation but shifts the problem of fuel production to converting and handling corrosive methyl bromide. The direct conversion of methyl bromide, at about 200 °C, into light hydrocarbons can be catalyzed under pressure by AlBr3 resulting in the formation of propane-rich mixtures of light hydrocarbons, carbonaceous deposits, and HBr. After releasing the gaseous products, the addition of hydrogen at 260 °C allows a quantitative conversion of the carbonaceous deposits into the same range of light hydrocarbons. These second-stage products efficiently contribute to the overall process yield while enabling a full regeneration of the catalyst′s activity. This oxygen-free process is compared to the conversion of methyl bromide on zeolites and the currently used methanol-to-gasoline (MTG) process in terms of product distributions and apparent energy of activation. A detailed chemical analysis of the intermediates revealed the presence of a carbon pool consisting of highly substituted benzene and cyclopentadiene derivatives, as observed on zeolites used in the MTG process. This similarity suggests that the currently used oxygen-based syngas/MTG process for methane conversion may be extended to a bromine-mediated process by using methyl bromide as an intermediate instead of methanol.